I don't know. Scarlet Witch and Medusa feel like incredibly left field ideas and less likely to get a spin off comic as much as say Widow or Marvel in the comics let alone the MCU (especially Medusa). Widow has already been in IM2 and Avengers that I'm not personally bothered about a solo for her right now.

Ms. Marvel I feel at least represents something that the MCU isn't currently offering and adds another potential strong female character for the Avengers.